1. Field of the Invention
The present invention generally relates to an image forming apparatus, an image processing unit, an image processing method, and a recording medium having an image processing control program, and more particularly relates to an image forming apparatus such as a digital copier, scanner, printer, facsimile, or a multifunction copier, and an image processing unit, image processing method, and recording medium having an image processing control program used in such an image forming apparatus.
2. Description of the Related Art
A multifunctional image forming apparatus having functions of a digital copier, printer, scanner, facsimile, and the like has been proposed (see, for example, patent document 1).
FIG. 20 is a schematic diagram illustrating an exemplary hardware configuration of a conventional image forming apparatus. In the conventional image forming apparatus shown in FIG. 20, functions of a scanner, printer, image processing unit, and the like are combined into an image processing engine 1000; and the image processing engine 1000 and a controller 1001 are connected via a general purpose bus 1002. The controller 1001 includes an operations display unit that is a user interface, an image data storage unit for storing processed image data, a communication unit for communication with external apparatuses, and a CPU that executes software programs for controlling the above units.
In the exemplary hardware configuration shown in FIG. 20, the controller 1001 communicates with an external apparatus and sends an image processing request to the image processing engine 1000; and the image processing engine 1000 performs the requested image processing. The controller 1001 stores processed image data in the image data storage unit.
As described above, in the exemplary hardware configuration, the controller 1001 communicates with an external apparatus and sends an image processing request to the image processing engine 1000 and a dedicated hardware unit of the image processing engine 1000 performs the requested image processing. Such a configuration improves individual processing efficiencies of the image processing engine 1000 and the controller 1001.
[Patent document 1] Japanese Patent Application Publication No. 2002-359743
The exemplary hardware configuration as shown in FIG. 20 has an advantage that since the image processing engine 1000 performs image processing, the controller 1001 is relieved of image processing load. However, since the image processing engine 1000 and the controller 1001 operate separately, it is difficult to make them interact to perform complicated image processing.
Especially, after an image processing operation is performed on image data and the image data are stored in the image data storage unit, it is difficult to perform another image processing operation on the image data. Thus, with a conventional image forming apparatus, only limited combinations of image processing operations are available.
Image processing operations, such as gamma processing, skew correction, and filtering, in an image processing apparatus are normally performed by hardware devices such as an application specific integrated circuit (ASIC) and a digital signal processor (DSP). An ASIC has a custom-designed circuit that provides, for example, a specific image processing function. Changing the image processing function of an ASIC requires changing the hardware itself. Therefore, in practice, it is difficult to change the function of or to add a function to an ASIC. An image processing function provided by an ASIC or DSP of the image processing engine 1000 may be implemented by software. However, since image data are stored in the image data storage unit and managed by the controller 1001, it is necessary to make the image processing engine 1000 and the controller 1001 interact to implement such an image processing function by software.